The present invention relates to magnetic disk records for data storage and to related systems; in particular it relates to a stacked array of flexible disks and related manipulating means.
As workers in the art know, the magnetic recording arts have developed swiftly since the 1950's and 1960's when they became commercially important. Workers in the art are familiar with the features of magnetic disks used for data storage, and in particular with the advantages of "flexible", or "floppy", disks. "Floppies" became commercially significant in the 1970's, offering a low cost medium, with acceptable "access time" (e.g., as opposed to magnetic tape systems).
"Flexible disks" can serve as a "unit record" medium that is compact, light, and is readily transported, stored, and handled, interchangeably with other like disks -- reasons why they are now widely used in the data processing arts. Thus, workers recognize that costs may be reduced in many cases by replacing a rigid magnetic recording disk with a "floppy" disk.
Floppy disks can be fashioned from well-known polyester sheet material (e.g., the familar polyethylene terephthalate used for magnetic tape) with a magnetic coating thereon -- this plastic being simply cut into the shape of a circular disk with a central mounting hole to accommodate the familiar drive-spindle. Such a "prior art" floppy disk is well known to workers and is shown and described in U.S. Ser. No. 711,647 filed Aug. 4, 1976, now U.S. Pat. No. 4,086,640, and hereby incorporated herein by reference to the extent relevant.
The present invention is directed toward improving the design of a pack of such flexible magnetic disks, as collected into a "floppy pack" and rotated at high rpm -- e.g., so that automatic pneumatic partition means may be employed to split the pack and expose any selected disk surface for Read/Write operations. An improved "floppy disk pack" according to the invention will be seen as particularly adapted for such partitioning -- using surprisingly simple means and methods, as described hereinafter.
Prior efforts with flexible disks:
Workers are familiar with prior approaches to the design and manufacture of floppy disks and to related equipment for handling them. Several are described in U.S. Ser. No. 711,647, now U.S. Pat. No. 4,086,640.
Workers are aware that for many floppy disk pack applications, it is of paramount importance to minimize pack cost while yet maintaining accurate, reliable operation. Thus, it is desirable to fabricate disk pack elements from commonly available, inexpensive means. It is particularly desirable to simplify the containment elements (e.g., end plates, spacers, and retainer means). The invention teaches this, and other techniques, using surprisingly simple, commonly-available expedients. For example, with the invention a set of disks may be stacked with a simple perforate spacer between each disk and a "flexible plate" at either end to produce a floppy pack affording the "pneumatic-partition" characteristics mentioned. Using a prescribed partitioning pack-hub, such a pack will exhibit such desired advantages as "self-pumping", "bistable selection-stability", "self-flattening", self-alignment, etc.
According to a further feature, such a flexible disk pack arrangement is also adapted for pneumatic selection using a very simple centrally-apertured hollow cylinder, one that is axially translateable and is coupled to the pack with a simple, novel flexure-hub centering coupling. Workers who appreciate the remarkable character of "floppy packs" in general will best appreciate these features and their surprising effectiveness, despite their surprising simplicity and unexpected versatility. For instance, it was quite unexpected that with pack elements so-simplified, one could nonetheless select any disk surface and partition with such high speed and fine precision, and yet readily maintain disk stability, even as-diverted.
The present invention is directed toward providing improved multi-disk record units which are better adapted to meet the foregoing problems and objectives in a manner satisfying minimum-cost objectives. The invention maintains the convenience of packaging a number of floppy disks in a convenient unit record file ("pack"), while prescribing improved simplified techniques for fabricating the pack.
There are other advantages to using flexible disk files; for instance, they may be operated to be "self-flattening". That is, unlike a rigid disk, a flexible disk which is spun fast enough will, of itself, flatten-out beautifully, correcting any static warp, etc. Flexible disks can also be "self-aligning". Where spindle misalignment (axis relative to a rigid disk plane) is usually a critical problem with rigid disks -- producing troublesome "runout" effects and adding to the complexity and cost of the disk drive (cost of bearings, correction means, etc.) -- it is usually not problematical for flexible disks. This is because centrifugal forces created by spinning a flexible disk at high rpm tend to correct any such misalignment. This makes it relatively easy and inexpensive to manufacture a flexible disk pack and the associated drive mechanism, as workers well know. According to a feature hereof, a pair of end plates are taught as comprising a simple stack of contiguous flexible disks which is "self-flattening".
Partitioning a "floppy pack"; prior art:
Workers have become greatly concerned over how to efficiently "partition" a stack of flexible disks; that is, how to displace and/or deflect the pack away from a selected disk surface to provide clearance for entry and manipulation of a transducer assembly. For instance, a "sliding piston" arrangement is disclosed in U.S. Pat. No. 3,130,393 to Gutterman. Gutterman uses externally pressurized air to "slide" the disks apart in a "forced piston" motion. However, most workers agree that a floppy disk file responds rather poorly to such partitioning forces.
In a related pneumatically-driven approach (see U.S. Pat. No. 3,618,055 to Van Acker and U.S. Pat. No. 3,509,533 to Krijan), air is pumped from "slotted spindle" into the stack. Along this line, some workers (e.g., see U.S. Pat. No. 3,867,723 to Penfold et al.) have felt that a radially-outward flow of pressurized air between adjacent disks had a stabilizing effect, especially when the flow is uniform about the pack circumference; accordingly, they have proposed providing apertured, or perforate, spacers between the stacked flexible disks to accommodate such an air flow.
For instance, in U.S. Pat. No. 3,969,767 to Griffiths et al. "spacer-washers" are proposed to separate disks in a disk file. Each "washer" is flexible and has a set of circumferentially-spaced axial projections serving to define ports for the exit of air radially from a central duct, the outward flow passing between adjacent flexible record disks which the spacers support. Such washers are further proposed as including an inner seat and made resilient to allow them to be clamped together and engaged for absorbing and controlling the forces holding the disk pack together. Such an array can be visualized as a laminated tubular "perforate-washer spindle", the semi-rigid washers being stacked to form an air-permeable spindle for coaxially supporting the pack.
The "disk location means" contemplated by workers for partition systems have involved a mechanical or optical referencing system. The mechanical system references the nominal position of each disk in the pack to a related fixed reference scale; the optical system employs a television type scan and means for continually "counting" disk position from a reference point in the pack. Both approaches are unduly complicated and troublesome. The present invention involves a departure from these approaches, using central-source pneumatic partitioning, providing a "pneumatic slotted hub" within the disk pack and shifting it axially to partition the pack. One may either position-reference the transducer mount relative to such hub movement or, preferably, hold the mount axially-fixed and partition widely enough to accommodate a large set of adjacent disks.
Fluid dynamics of disk partitioning:
It has been found that so using a "hollow-hub" supplying pressurized air between disks in a floppy pack, disturbance of nominal pneumatic forces between "stable" disks can serve to control volumetric air flow between the disks. That is with inter-disk air flow equal, the disks tend to stabilize in equidistant relation; whereas selectively increasing air flow between a particular disk pair will tend to thrust that pair further apart. Also, interrupting such a radially-outward air flow between disks tends to pull them together and hold them somewhat compressed.
In light of such observations, and as a principle feature, the instant invention teaches providing a stack of flexible disks with a certain rigid apertured spacer between each disk, together with a central pneumatic separator-hub arrangement and an associated transducer mount. This hub is preferably cylindrical, hollow and axially translateable, with a transverse gap intermediate its length -- the gap adapted to generate the desired radial "air-jet" between selected disks for "partitioning". Such a "jet hub" is thus adapted to be accurately translated along the inner hollow axis of the mentioned stack and to be selectively positioned so as to direct this partitioning air jet to displace any two adjacent disks.
Moreover, according to this feature, it has been found that such an arrangement can "pump" its own air flow and establish such a partitioning-jet without need for any separate pumping means. It can also direct the jet between a selected disk pair to quickly and accurately move down the pack, "toggling" disks from one bistable condition to another (e.g., "flat" to "divert-up" to "divert-down") -- all conditions being stably held until upset by a new positive force. Such an arrangement has been found to offer considerable advantsges where rapid, reliable separation is required at high disk rpm, especially for relatively thick packs (e.g., several hundred disks).
Workers contemplating such flexible disk packs have also been concerned over the problems of transducer/disk engagement. Now, at the high disk rpm contemplated with the invention, the head must be "flown" over a disk surface (as opposed to "contact recording" which is feasible only at lower disk velocities"). Now while a single flexible disk can nicely conform to the configuration of a flying head, a stack of them cannot easily do so. Workers recognize that (unlike rigid media) a flexible disk will be compliant to head engagement, but that this compliance will vary with the number of subjecent disks (under the selected disk surface). Thus, as described below an arrangement has been found that gives the described partitioning as well as accommodating an air-film between all disks, continually, for separation thereof -- these being adapted to accommodate relatively low disk/head engagement forces (e.g., up to about 10 grams). Surprisingly, and fortunately, the use of such transducer arrangements with such flexible disk media has been found to closely approximate the operation of magnetic tape systems and to afford similar advantages, such as relatively long life for the head and media.
As mentioned, the flexible disk packs and associated manipulating mechanisms according to the invention are particularly apt for "high speed" systems. Such "high speed" systems will be better understood from the parameters recited herein (e.g., see Table I below, by way of example, but not limitation).
Thus, the invention may be generally understood as involving an improved pack of flexible recording disks held in a prescribed stack between air-permeable spacers and adapted to be partitioned pneumatically with central hollow cylinder means directing an air jet radially out through a prescribed registering "crenelated" spacer, the spacer location corresponding to the desired inter-disk partition desired.
In a preferred form, a stack of magnetic recording memory disks is assembled with each separated by a "crenelated" (see below) spacer rings, the array clamped between resilient end plates to comprise a pack adapted to be mounted upon a turntable in operative relation with a central partitioning cylinder. This cylinder is resiliently coupled to the pack, preferably through adjustable centering hub-flexure means, and adapted to be thrust axially and "self-returned".
The (usually partial) partitioning effected by this pneumatic assembly is such as to admit entry of a prescribed transducer mount which is adapted to further deflect the disk pack and complete partitioning, while carrying magnetic transducer means into operative contact with the selected disk surface.
This transducer mount may enter the pack along a single prescribed plane, or, instead, be axially positionable to register with the plane of the selected disk, the partitioning means accommodating either mode. For example, it may divert the pack about one single "transducer plane" no matter which disk is selected.
In particular it will be seen that the embodiments including a novel arrangement of end plates which are made flexible and "self-flattening", preferably comprised of stacked contiguous "floppy disks". The spacers preferably comprise "crenelated washers" allowing a certain partitioning radial air flow. According to certain other related features the pack is resiliently coupled to the pneumatic-partitioning cylinder and its associated positioning means and is adapted to resiliently engage transducer mounts and associated magnetic transducer means. Workers will contrast such an arrangement with prior art designs such as those shown in U.S. Pat. No. 3,969,767 to Griffiths, et al. where, for instance, a disk pack is contained between rigid end plates and a different spacer arrangement.
The foregoing and other features, objects and advantages according to this invention will be more fully appreciated and become more apparent upon consideration of the following description of preferred embodiments taken in conjunction with the attached drawings, wherein like reference indicia denote like elements.